1. Field of the Invention
The present invention relates to a contour line measurement apparatus for measuring a three dimensional contour line shape of an object by using a stereo camera, and a robot system.
2. Description of the Related Art
To perform various operations on a workpiece by using an industrial robot, recognizing a three dimensional contour line shape of the workpiece is required. When the workpiece has no individual difference, information on a contour line shape of the workpiece can be obtained on the basis of design data. However, for example, when the workpiece is a cast, the workpiece has an individual difference for each casting mold, and consequently measuring a contour line shape of each workpiece is required.
Regarding this point, conventionally, an apparatus in which accurate three dimensional contour line information is obtained by a stereo method using two cameras (for example, Japanese Laid-open Patent Application No. 2012-202732 and Japanese Laid-open Patent Application No. 2013-130508). In apparatuses disclosed in Japanese Laid-open Patent Application No. 2012-202732 and Japanese Laid-open Patent Application No. 2013-130508, two cameras each capture a picture of a workpiece from positions different from each other, and from a pair of pictures thus obtained, each edge line (image of contour line) is extracted. Subsequently, intersections of epipolar line each obtained on the same epipolar plane and the edge line on each picture are determined. Then, the intersections on each picture are associated with each other, and these corresponding points are used to determine a position of three dimensional points on a contour line of the workpiece.
However, in the apparatuses disclosed in these Patent Documents, when there are a plurality of edge lines which intersect with the epipolar line, the lack of one-to-one correspondence between intersections in each picture makes determining the corresponding points difficult.